Women who undergo the surgery have both of their ovaries removed before they experience natural menopause, the procedure is called oophorectomy. The reasons for removing the ovaries may be because of vaginal bleeding, cancer of the uterus or ovaries, or fibroids. When the ovaries are removed the production of estrogen is completely stopped.
The study suggests that there is a link between oophorectomy and a decline in cognitive ability. It also found that women who undergo the surgery and are then be put on extensive hormone therapy aren't affected as much.
According to the author of the study, Riley Bove, MD, with Harvard Medical School in Boston and a member of the American Academy of Neurology:
"While we found a link between surgical menopause and thinking and memory decline, women on longer hormone replacement therapies had slower declines. Since hormone replacement therapy is widely available, our research raises questions as to whether these therapies have a protective effect against cognitive decline and whether women who experience early surgical menopause should be taking hormone replacement therapies afterward."
The purpose of the study was to further understand why it is that reproductive factors have an affect on cognitive ability. There is already a lot of evidence linking lower levels of estrogen with a decline in mental ability.
A total of 1,837 women (aged 53 to 100) were analyzed, of whom a third had undergone oophorectomy. The team recorded the frequency of their menstrual cycles, the age of their first menstruation and the length of hormone replacement therapies. They then gathered results from memory tests and over 500 brain biopsies to see whether there might be a link between the surgery and poorer mental ability.
Oophorectomy linked to mental declineThe researchers found that the earlier the age of surgery, the faster the decline in memory and overall cognitive ability. This was consistent with factors such as education, age and whether they smoked. They noted that this link was not identified among women who reached menopause naturally.
However, there is still more research necessary before any concrete claims can be made regarding the data from the study.
Dr Bove concludes: "Our study warrants further research as the interest in this subject will continue to grow right along with our aging population."
This isn't the first study to warn about the possible health effects of surgically removing the ovaries, a study presented at the 2011 CTRC-AACR San Antonio Breast Cancer Symposium associated the procedure with higher prevalence of low bone mineral density and arthritis.